1. Field of Invention
The present invention generally relates to an apparatus and method for the installation of a repair material within a conduit or pipe such as a sanitary sewer line. More specifically, the invention pertains to an apparatus and method for the installation of a repair material controlled from a remote location using fluid pressure and electrically resistive or impedance heating to deploy, form and cure the repair material to the inside surface of a pipe.
2. Description of Related Art
It is generally accepted that the aging infrastructure worldwide is fast approaching originally designated design lives. Specifically, pipes and conduits located both above and below ground employed in the conveyance of liquids frequently require repair to prevent leakage into or from the pipe system. The cause of leakage can vary from improper installation to environmental conditions to normal aging or the detrimental effects of the substances transported on the pipe materials. Regardless of the cause, leakage is undesirable.
Because of the high costs and the level of difficulty involved in excavating or removing and replacing leaking conduits, various methods have been devised for insitu repair. These methods have minimized the expense and hazards associated with digging and replacing defective pipes.
In the conventional processes for the insitu rehabilitation of existing pipes and conduits, a flexible tubular liner impregnated with a thermosetting synthetic resin matrix is introduced into the conduit using an inverting process as well know to one skilled in the art. In U.S. Pat. No. 5,108,533, the flexible tubular liner is comprised of a needle-punched felt material.
Once the liner is positioned within the pipeline, the liner is pressurized internally using a fluid pressure such as air or water to force the lining material into intimate contact with the pipe interior and provide compaction. Adding heat in the form of hot water, steam or electrical energy can then cure the resin matrix. The latter method of providing heat by electrical energy is disclosed in U.S. Pat. No. 5,606,997. Once the resin is cured, the resultant material forms a hard, tight fitting lining within the pipe that also serves to provide added structural support.
Only several processes are known that address in situ repair of pipe wall. One such process is described in U.S. Pat. No. 5,223,189 for repair of the interface between two pipes, such as sewer main line and an intersecting lateral line, wherein a thermoplastic sealing material is installed into the a pipe by means of a robotic device and an expandable mandrel. This method relies on a heat formed seal being produced between the repair material and a pipe. In U.S. Pat. No. 5,950,682, a resin absorbent material, impregnated with a hardening resin matrix, is positioned within the mainline pipe and provides a means for inverting a section of like material into the lateral pipe for a pre-determined distance. Some of these techniques require access to the pipe interior from two spaced locations. This is not often possible.
In addition, because these processes use a resin matrix that is expected to fully cross-link or cure in an undesirable environment (i.e. hot, cold, wet, etc), catalysts, initiators and even inhibitors are added to the resin system in an attempt to control the curing mechanism. This has resulted in many failures due to premature curing of the resin, inadequate resin cross-linking and shrinkage. In addition, because the resin is applied to the repair material at the installation site (and typically in uncontrolled conditions), inconsistencies in resin content or mixing procedures, inadequate resin distribution within the repair material, and premature resin curing can be expected. Other methods have been disclosed that use an auxiliary curing source unlike the typical systems that rely solely on ambient temperatures to effect a cure. Radiant energy in the form of ultraviolet light, as in U.S. Pat. No. 5,915,419, or visible light, as disclosed in U.S. Pat. No. 4,518,247 have been employed to provide a curing mechanism for lateral interface sealing systems. The shortcomings of these types of systems lay in the difficulty of the prescribed radiant light source to penetrate through the thickness of the repair material and the overall fragility of such devices.
Therefor, it is desirable to provide a system to overcome the constraints mentioned above and also afford a fast, consistent repair method that enables robust, cost effective in situ repair of pipe walls.